1. Field of the Invention
This invention relates to well tubing handling systems, and more particularly, but not by way of limitation, to a snubbing apparatus used for running and pulling well tubing through a wellhead under pressure.
2. Brief Description of Related Art
Well tubing handling systems employed in running and pulling well tubing under pressure, particularly, for well workover operations, have been known for many years. Such well tubing handling systems are commonly known as “snubbing units.” It is common practice to use cable and pulley arrangements and hydraulic cylinders, both alone and in combination, for lifting well tubing from a well and for pushing the well tubing downwardly into the well against well pressure. Some such systems are mounted on and supported solely from the wellhead structures, while others involve the use of substantial platform structures, including derrick type frameworks.
An important factor in the operation of well snubbing units is the cost of servicing a well with the apparatus. Such cost is often directly related to the length of time the well is shut down and, thus, not producing an income, and the length of time the well is shut down directly corresponds to how long the snubbing operation takes. Many factors dictate how long a snubbing operation will last. One of these factors includes the depth of the well. However, other factors directly related to the snubbing apparatus include the length of its stroke and its lifting capacity. Clearly, a snubbing apparatus with a short stroke length will require a greater number of cycles to run or pull a given length of well tubing.
Another factor in the operation of well snubbing apparatus is getting the apparatus to the well site. Many wells have been drilled in environmentally sensitive areas not easily accessible by land vehicle. For example, many wells have been drilled in offshore locations or in swamp lands. Prior art snubbing apparatus are typically trailer mounted eliminating the ability to operate in offshore or swampy areas. For snubbing apparatus that might be sized to be transported by water vehicles, a downsized version may be a limiting factor with respect to the length of the stroke of the device and the amount of weight the unit can lift, thereby increasing the cost of operating such a snubbing apparatus.
To this end, a need exists for a compact snubbing apparatus that is capable of being mounted to a vehicle which is capable of accessing wet areas, such as a barge or swamp buggy, while not sacrificing power or stroke length. It is to such a snubbing apparatus that the present invention is directed.